This is a revised proposal to study the effects of introducing a Computerized Admission Testing System (CATS) into the Emergency Department (ED) of a large urban teaching hospital. CATS is an outgrowth of admission testing guidelines published in Common Diagnostic Tests. Use and Interpretation, produced by the American College of Physicians in collaboration with the national Blue Cross Blue Shield Association. Preliminary studies using CATS have indicated that its recommendations could reduce the volume of routine admission testing by approximately 50%. A randomized controlled trial will be performed to compare three admission testing protocols for patients admitted to Medicine through the ED. The patients in Study Group A will have all tests in a designated battery performed, patients in Group B will have those tests performed that are requested by the physician on the inpatient floor (usual practice); and patients in Group C will have only those tests performed that are recommended by CATS. Data will be collected to ascertain CAT'S' recommendations for all three groups. The basis for group assignment will be the group practice 'firm' link at MetroHealth Medical Center (Metro), where ongoing random assignment of patients and physicians has been in effect for almost a decade. Approximately 470 patients will be admitted to each firm during the six months of patient entry into the study, and all patients will be followed for two months after hospital discharge. Aims #1-3 reflect short-term goals of this project, and Aim #4 reflects pilot data needed to perform a more comprehensive evaluation of practice guidelines for routine admission testing. Aim 1. To determine the effect of CAT'S on the number of 'routine' tests ordered on admitted patients as compared to usual admission testing practices. Aim 2. To estimate the savings in routine admission testing costs associated with using CATS. Aim 3. To assess the safety and inpatient physician acceptance of using CATS for admission testing. Aim 4. To pilot test methods to accurately and reliably capture the costs and outcomes of admission test-related follow-up evaluation, and to determine the population-based variances in resource use required to design a more comprehensive investigation of CATS. Whether a more discriminating approach to admission testing would produce substantial cost savings (as thought by many) and equivalent or better medical outcomes (as hypothesized by the investigators) is not known. The ultimate goal of this project is to examine this question and to rigorously test a promising approach to implementing the guidelines of experts.